Strawberries and bananas should make an excellent combination.
I have made a lot of strawberry wines and it is a great success during summer.
The strawberries will provide flavor and the bananas will give the wine some body. No need for additional ingredients, except like Wade already said: sugar some acid and some nutrients.
I presume you do have a hydrometer.
Do as Wade said with dilluting the juice but I would do some tasting along the way. I would not make it to thin.
Then adjust sugar to get a wine of about 11% alcohol, that is about right for strawberries. Bring the acid up to about .6 and you will have a great rose this summer......
To keep the freshness I use citric acid.
It will even be better next year.
Oh, and before I forget. Look at the packaging and make sure there
are no things like sorbate, benzoate or excess sulphites in the juice
otherwise it will be hard to ferment.
Luc